What is true altitude?

True altitude is defined as the height above mean sea level (MSL). This measurement is crucial in aviation as it provides a standardized reference point for altitude that pilots and air traffic controllers use to ensure safe separation between aircraft.

Mean sea level is considered a consistent baseline from which various altitudes can be measured. The use of MSL allows for accurate navigation and positioning across different geographical locations and under varying atmospheric conditions.

While height above ground level and altitude measured by barometric pressure can be relevant in specific contexts—such as when determining a plane's distance from the ground or its altitude during landing and takeoff—true altitude specifically refers to the height in relation to mean sea level. Altitude calculated from GPS data can provide positional information, but it may not always align with true altitude if not adjusted for MSL. Thus, true altitude remains the standard for aviation operations and safety.